This game in my honest opinion is the most balanced it's ever been between factions, even if the economy etc. still need some tweaks to improve gameplay. The idea was floated of increasing the HP of all line units by 10-20% to make game pace more manageable for newer players. I think this would come at the cost of completely resetting the balance that has been achieved in game by modifying unit abilities damage. In my opinion the nerf of flamers was one of the most important for making Eldar strong again. What's changed is that now T1 and T2 upgrades are actually sufficient to survive a lot of threats that were providing clutch early victory for some players, in particular macha, weirdboy and flamers.
If you increase all unit health infantry in endgame will have a huge amount of HP. Any changes to the health of units should be done by changing the amount of health given by infantry upgrades, perhaps buffing health 1 and nerfing the previous two so that early health upgrades give a counter to high burst damage in early game.
In my opinion, a blanket change to infantry HP would cause more problems than it would solve and be extremely strange for current players without necessarily improving the game in any way that couldn't be done more subtly.